1. Field of the Invention
The present invention generally relates to a video processing technology, and more particular, to a method and a system for determining a video deinterlacing strategy.
2. Description of Related Art
Conventionally, in order to convert an interlaced video into a progressive one, there are three existing deinterlacing methods available: the first method commonly referred to as “bob”, the second method referred to as “weave” and the third method referred to as “adaptive motion”. In the “bob” method, every field is expanded into a complete frame, wherein the lost line data between any two adjacent scan lines in the field is filled up with the data obtained by interpolating the previous line data and the following line data thereof. As shown in FIG. 14, in order to deinterlace the first field 1401 or the third field 1403, the data of the even lines are used to interpolate the data of the odd lines; in the same way, the data of the odd lines are used to interpolate the data of the even lines so as to deinterlace the second field 1402 or the fourth field 1404. However, the resulting image using “bob” appears to be a variegated mosaic. Even after a proper processing, the image still has a soft-shifted look with an unavoidable resolution loss. In the “weave” method, two adjacent fields, an even field and an odd field are synthesized into a complete frame, i.e., with the algorithm, any two continuous fields are combined into a frame. As shown in FIG. 14, the first field 1401 and the second field 1402, or the second field 1402 and the third field 1403, are combined to form a complete frame. The “weave” method is usually suitable for the situation where the inter-field motion is dinky, for example, for the two continuous fields of a movie frame. However, for the two continuous fields with an inter-field motion, the synthesized frame looks to have combing artefacts.
The “adaptive motion” method is a compromise between the “bob” method and the “weave” method, which includes the advantageous features of the two methods, wherein a motion detection processing is conducted on all the pixel points of the received field, wherein when a pixel point is judged to be in still by the detection, the “weave” deinterlacing is conducted on the point so as to obtain the optimum resolution result, and when a pixel point is judged to be in motion, the “bob” deinterlacing is conducted on the point so as to avoid the combing phenomena. Hence, the quality of the deinterlaced frame by using the “adaptive motion” method mainly depends on the motion detection capability.
In the prior art, there are two schemes of motion detection, namely frame motion detection and field motion detection. FIG. 16A is a diagram showing the conventional frame motion detection method. Referring to FIG. 16A, there are four fields F161-F164 herein. According to the frame motion detection method, the pixels 1601 and 1602 located at the same position in the same fields (for example, F162 and F164) are judged whether they are in motion. When the differential value of the pixels 1601 and 1602 is greater than a preset value, the pixel 1602 would be judged to be in motion, and the pixels 1602 and 1603 are accordingly used for conducting a “bob” algorithm to obtain a pixel 1604.
FIG. 16B is a diagram showing the conventional field motion detection method. Referring to FIG. 16B, there are also four fields F161-F164 herein. According to the field motion detection method, in order to judge whether the pixels 1605 and 1606 in a field F161 are in motion, the pixel 1607 adjacent to the pixels 1605 and 1606 in the field adjacent to the field F161 (for example, F162) is used. When the differential value of the pixels 1607 and 1605 and the difference value of the pixels 1607 and 1606 are greater than a preset value, the pixel 1607 in the field F162 and the pixels 1605 and 1606 in the field F161 are judged to be in motion; otherwise, they are judged to be still. For the “still” judgement, a “weave” method is applied, that is to say, the pixels 1605 and 1606 would directly combine with the pixel 1607.
However, there are a couple of problems in the above-mentioned conventional motion detection schemes in selecting a proper deinterlacing algorithm. FIG. 1 is a diagram of conventional virtual still, wherein 101 and 103 are odd fields, while 102 and 104 are even fields. It can be seen that the sampled points on the sunroof in the fields 103 and 101 along a sampling trace 105 appear white, while the corresponding sampled points in the fields 102 and 104 appear black. If the frame motion method is used to compare the adjacent odd fields (for example, the field 101 is compared with the field 103) or the adjacent even fields (for example, the field 102 is compared with the field 104) herein, the wrong comparison result of “still” would be given, which leads to combination of the fields 101-104 in FIG. 1 and results in the field result as shown by 202 in FIG. 2. In the field 202 in FIG. 2, a serious combing occurs with the sunroof portion. On the contrary, if the field motion method is used to compare the adjacent odd and even fields (for example, the field 101 is compared with the field 102, or, the field 102 is compared with the field 103) herein, the comparison result of “in motion” would be given, which leads to conduct the “bob” algorithm on the fields of FIG. 1 and results in the field result as shown by 201 in FIG. 2 where no combing occurs with the sunroof portion at all.
FIG. 3 is another diagram of conventional virtual still, wherein 301 and 303 are odd fields, while 302 and 304 are even fields. It can be seen that the sampled points on the “O” mark in the fields 303 and 301 along a sampling trace 305 appear white, while the corresponding sampled points in the fields 302 and 304 appear black; on the other hand, the sampled points on the “K” mark in the fields 303 and 301 appear black, while the corresponding sampled points in the fields 302 and 304 appear white. If the field motion method is used to compare the adjacent odd and even fields (for example, the field 301 is compared with the field 302, or, the field 303 is compared with the field 304) herein, the wrong comparison result of “in motion” would be given, which leads to conduct the “bob” algorithm on the fields 301-304 of FIG. 3 and results in the field result as shown by 401 in FIG. 4 where a serious flicker artefact occurs with the “OK” mark.
In short, if the conventional frame motion is conducted on the adjacent same fields (odd fields or even fields) to judge whether a frame is “in motion”, then, for the case of the input fields 301-304 of FIG. 3, the right result as shown by 402 in FIG. 4 is expected (no flicker at all); for the case of the input fields 101-104 of FIG. 1, the wrong result as shown by 202 in FIG. 2 is obtained (serious combing). If the conventional field motion is conducted on the adjacent different fields (odd and even fields) to judge whether a frame is “in motion”, then, for the case of the input fields 101-104 of FIG. 1, the right result as shown by 201 in FIG. 2 is expected (no combing); for the case of the input fields 301-304 of FIG. 3, the wrong result as shown by 401 in FIG. 4 is obtained (serious flicker).
Obviously, the conventional technology is limited to deal with one of the above-mentioned cases, FIG. 1 or FIG. 3, and the prior art fails to deal with both the cases simultaneously and correctly. However, in order to obtain the optimum result in practice, any wrong judgement must be avoided; that is to say the case of FIG. 1 and the case of FIG. 3 must be judged as “in motion” and “still”, respectively.